The psychology of the missing 30 millilitres

At a recent family dinner, my almost 26-year-old was staring at his can of soft drink in amusement. His action annoyed me, so I said in a light joke, 'someone is preoccupied today.'
With a big smile lighting his face, he announced his great discovery: “The amount of drink in this can dropped from 330 to 300 ml for the same price”.
We all looked at our cans more carefully. He was right. Thirty millilitres had quietly disappeared. Not enough to dramatically change the size of the can. Not enough for most people to immediately notice. Yet over time, multiplied across products and purchases, it adds up.
The marketing world calls this phenomenon: shrinkflation, which means rather than increasing prices directly, companies reduce the quantity of a product while keeping the price unchanged.
Consumers often react more strongly to seeing a higher number on a price tag than they do to a slightly smaller package. A few grams less here, a few millilitres less there, and many of us continue buying without questioning it.
What fascinated me was not the economics behind it, but the psychology.
Human beings are not as observant as we like to imagine. We assume we notice changes around us, yet our minds are surprisingly selective.
Psychologists have long studied something called 'change blindness,' our tendency to overlook gradual or subtle changes in our environment.
In classic experiments, people often fail to notice major alterations in scenes directly in front of them if those changes happen gradually or under distraction.
Perhaps this is because the brain is designed for efficiency rather than accuracy. If we paid attention to every detail around us, we would be overwhelmed. Instead, the brain filters information and focuses only on what appears immediately important. The downside is that many changes slip through unnoticed.
And this does not happen only with soft drink cans.
Many of the important changes in life arrive quietly. Stress does not usually appear overnight.
Relationships rarely collapse in a single dramatic moment. Burnout often develops through tiny daily adjustments; you start sleeping a little less, worrying a little more, spending a little less time with your family, and postponing rest because work feels urgent. One day, people suddenly say, “I don’t know what happened. I just feel exhausted.”
But often something did happen, but we simply did not notice it.
The same is true of happiness. We sometimes expect joy to arrive in grand moments such as promotions, achievements, or life-changing events. Yet much of life’s satisfaction also changes gradually.
We stop noticing simple pleasures like family dinners, conversations, routines, and familiar faces around us. Like the disappearing thirty millilitres, small things slowly fade from awareness.
My son eventually returned to his dinner, munching his kabab quietly and feeling pleased with his discovery. I smiled quietly, realising that perhaps he had noticed more than a marketing strategy. He had accidentally pointed toward an uncomfortable truth about human nature.
Sometimes life does not change through earthquakes. Sometimes it changes through missing thirty millilitres at a time. And perhaps psychological wisdom begins with occasionally pausing long enough to look more carefully at the can in our hands.